1. Field of the Invention
The present invention relates to a lens and a method for manufacturing a lens. Specifically, it relates to a lens including a light incident surface having a shape determined by a certain design method and a method for manufacturing such lens.
2. Related Art
Recently, a development of a semiconductor light emitting element such as an LED (Light Emitting Diode) has advanced and a use of such element has been enlarged. Such semiconductor light emitting element generally includes a light emitting portion having a flat shape. Here, in order to obtain a lens capable of forming a desired light distribution pattern making effective use of the shape of the light emitting portion of such light source, US-2005-0086032-A discloses a method in which a large number of span points existing in common in respective light incident and outgoing surfaces are defined first to thereby determine respective shapes of the light incident and outgoing surfaces. Further, JP-H03-174109-A discloses a technology which firstly determines a shape of a light incident surface and thereafter determines a shape of a light outgoing surface.
According to the technology disclosed in US-2005-0086032-A, the shapes of the light incident surface and light emitting surface are simultaneously determined. However, it is difficult to determine the shape of the light outgoing surface while taking the space and design thereof into consideration. Thus, from a viewpoint of realizing a high degree of freedom of design when designing a lens, there is room for improvement.